Today, flat roofs are prior art in industrial as well as residential buildings. Insulating layers (e.g. insulating foams, insulating panels, glass and rock wool) are thereby typically applied to a statically load-bearing subsurface of profiled metal sheets, a wooden substructure or concrete surface, and they are covered with sealing membranes, which are laid in the form of webs. On the one hand, these sealing webs (in the alternative also referred to as material web, roofing sheet, roof film, film web) need to be welded to one another on the seams, on the other hand, they also need to be fastened to the subsurface, because any air flow, which sweeps across the surface, effects a buoyancy, which lifts the sealing web. The initially common seal fastening provided for only the seam of the sealing web, which had just been laid, to be fastened to the support structure through the packet of insulating layers. The next web is then welded to the prior web to overlap in such a way that the fastening points of the prior web are also covered under the new sealing web. To reduce the number of the sealing webs and thus the running meters of welding seams, sealing webs of increasing widths were used, which, however, moves the fastening seams further and further apart from one another.
The field fastening was thus developed as alternative for the seal fastening. In the case of a laying method, which is known on the market, the fastening elements of the insulating layers are thereby also used. These fastening elements often consist of long screws or bolts, the first end of which is introduced into the substructure and which, on the other (second end), have a head comprising a washer-shaped widening, which bears on the insulating layer and secures the latter. These head disks or load distribution disks, which have a diameter of several centimeters, preferably made of metal, distribute the tension, which emanates from the fasteners, which are attached in a punctiform manner, in a flat manner. The head disks are suitable as fastening points for the films (material webs); for this purpose, they are coated with a thermoplastic or with a hot-melt adhesive material. After the fastening of the insulating layers, the roof films or sealing webs, respectively, can be unrolled. At those locations, where the head disks are located, the metallic head disk is heated through the web by an induction unit, whereupon the applied adhesive effects a flat heat seal between the underside of the sealing web and the head disk.
It is a secondary condition hereby that a contact pressure needs to be ensured during the cool-down phase to achieve an intensive and resilient adhesion.
In response to the manual laying according to the above-described method, the position of the head disk below the sealing web is determined by a sensor (inductively, magnetically, . . . ) and the induction heater is placed accurately. After the heat-up phase or after successful welding process, respectively, the heater is replaced by a cooling element. This can be a simple metal body, which, due to its mass, ensures the contact pressure and serves to dissipate heat. The cooling element can also comprise a magnet, which supports the holding and clamping process. It is a disadvantage that the processing process requires a plurality of cooling elements, which need to be installed according to progress and which need to be gathered up again after the cool-down phase.
Further known problems are that the locating of the head disks, which are invisible below the seal, is extensive and that the placement of the induction unit as well as of the cooling elements requires experience. It is possible to overlook head disks because they cannot always be installed at regular intervals and patterns, because a roof surface can have lead-throughs, dormers, overhead lights, vents or other superstructures and installations.
This work, which is demanding and monotonous at the same time over a long period of time, with long wait times, thus quickly became the reason for efforts to automate the process.